I was wondering about the conditions there, so I did a little Google search. The bridge is just below the dam. The dam's water output fluctuates over the course of the day, so at times the clearance under the bridge is pretty good, like in this picture: http://www.dickestel.com/images/pinefl3.jpg

and at times, it is pretty tight. http://www.krcd.org/image/1a.jpg

Below is a picture that appears to show a prime kayak launch site. This is just downriver of the bridge. All boating and swimming is prohibited, and I bet that's what these signs say. I wonder why they make it so easy for people to launch boats here, if it's forbidden. I wonder if conditions changed on the first kayaker after he launched, and if he got trapped there when floodgates were opened. I also wonder if they could have turned the dam off if they saw someone trapped under the bridge, or if there is a spillway that always has a water flow. It would be neat if they could just turn the water off to let the trapped kayaker walk out of a dry river bed to safety.

I guess none of it matters much. If the first kayaker had to walk past these signs to put into the water, he is fully responsible for the death of his rescuer.